Valves for use with vacuum equipment are essentially different from valves used in conventional systems whose objective is to control the flow of a liquid or gas. In such conventional systems, some leakage of the liquid or gas can usually be tolerated. In the case of vacuum valves however, even the slightest leak involves not merely the loss of a liquid or gas, but total destruction of the vacuum in the vacuum equipment controlled thereby.
In addition, vacuum destroying gases originate not only through leaks in the valves, but also from the materials used in the construction of conventional valves. For that reason, it is most desirable to use all-metal valves in conjunction with vacuum equipment. Specifically, it is not feasible to use organic materials for the seals of valves to be used in conjunction with high vacuum systems.
All-metal valves have been produced in the prior art for use with vacuum equipment, and such valves usually comprise a metal gate which is moved at right-angles to the orifice to be closed thereby, between an open position and a closed position. Such valves usually include appropriate means for causing the gate to be sealed against a seat surrounding the orifice, when the gate is in its closed position.
The present invention provides an improved construction for such a valve in which mechanical linkages and mechanisms required to actuate the gate are minimized, and in which the valve gate is activated and forced against the seat around the orifice by means of a simple fluid actuated mechanism which requires a minimum of moving parts.
The valve of the invention is mounted in a hermetically sealed valve housing which is evacuated so as to reduce the pressure differential across the gate-seat seal to a minimum so as to obviate any tendency for molecular leaks to occur across the seal.
All-metal seals are used in the valve of the invention, so that the assembly may be entirely formed of metal, and so that the assembly may be free from organic materials which could destroy the vacuum within the equipment with which the valve is used. Moreover, the valve of the invention may be operated in wide extremes of ambient temperatures without destroying the seals between its gates and their seats. Moreover, the valve of the invention can be placed in areas where high levels of radiation occur which would otherwise damage organic seals, and the like, and cause them to give off gases or vapors.
The sealing edges of the gates in the valve of the invention are relieved, so that when the gates are closed and forced against the corresponding orificies by internal fluid pressure, the outer edges of the gates are deflected, and the resulting resilient stress of the gates against the seats causes the gates to be held firmly against the seats even in the presence of thermal expansion or contraction.
The gates and seats of the valve in the embodiment to be described are formed of relatively hard metal such as stainless steel, and a layer of relatively soft metal, such as copper or gold, is deposited around the peripheral edge of each seat, or on the adjacent portion of each gate, so as to constitute a seal.